Despite the highly conducive weather of the past three weeks, blue mold had not been reported from anywhere in the Ohio River Valley or Tennessee River Valley as of May 13. The burley and dark tobacco production areas have been very fortunate during this protracted wet period in that the winds have prevailed from the south, rather than the southeast where blue mold is active in flue cured production. This southerly route has much less potential to acquire and maintain viable spores before reaching us, thus greatly reducing the potential for blue mold in our region if this is the only route of spore introduction.
Also, there is no evidence available to us that blue mold has been imported into the region on transplants this season or that it has over-wintered here. Considering the weather of the past three weeks, had the pathogen been introduced with plug-plants, by now it probably would have been widespread in those plantings and into surrounding communities. However, shipments of finished plants from the southeast may have been delayed, and may yet arrive.
Significant blue mold activity is occurring in flue cured tobacco from Florida into southern Virginia. That blue mold is a threat to our region under two conditions. One, we import plants from those areas. Or two, there is a change to easterly or southeasterly winds. Basically, we have blue mold on our east flank and as long as the disease is active there, we need to be prepared to react quickly to a change in winds coming from the southeast or east. So stay in touch, frequently and regularly, with the warning system if you are relying on it for current information to help with your decisions.
Transplanting to the field in our region has been slowed markedly due to frequent and heavy rains, increasing the potential staging areas for blue mold and other diseases to develop. Adequate fungicides are not labeled to protect against all the diseases that could develop under these conditions. Thus, growers are urged to take steps to reduce leaf moisture through careful management of ventilation (get air to them to help dry the leaves and stems) and keep in place a regular fungicide spray program. Regular fungicide spray schedules should be maintained in all transplant production systems - See issue 943 of Kentucky Pest News (March 18, 2002) Weekly fungicide sprays in the field are not warranted at this time for blue mold control, based on the information available to us, unless a southern transplant connection exists with the crop. However, crops should be scouted twice weekly for evidence of bacterial and fungal diseases. If sprays are needed, see issue 948 of Kentucky Pest News (April 22, 2002) for the foliar fungicide options labeled in Kentucky for use in the field. For example, during the past week scouts have found serious angular leaf spot in early-set burley fields and streptomycin sprays were made to slow disease development. In another case, the grower suspected the yellow spots were blue mold and was preparing to spray fungicides, but we concluded it was hail injury.
For the latest blue mold status and other tobacco disease information, check the KY Blue Mold Warning System.
http://www.uky.edu/Agriculture/kpn/kyblue/kyblue.htm
Some are claiming that Terramaster, especially the 4EC
formulation, used at labeled rates is causing a sudden death
and slimy rot within a few days. These symptoms resemble
some aspects of Pythium root rot, but are not identical.
Essentially what appears to be happening is that "healthy water
roots" become suddenly, limp, translucent and with a slimy rot
that darken within a few days from grayish to brown. This
slimy mess is confined to those roots hanging in the water and
usually does not extend up into the root ball, but when it does,
is confined to a small portion in the bottom of the cone. The
top
growth is reportedly often slowed and yellowing, but that
complaint is less common. Universally, the claim is that within
a few days, new white roots emerge unless more serious
problems are involved.
Some researchers have reported that this is a symptom of Terramaster injury, and some claim they see it every time they have made a treatment of Terramaster and never see it in their checks (untreated plots). Others report that they have occasionally observed these symptoms in both the treated and untreated plots, but that it is rate dependant, being worse with the plots receiving higher rates of chemical. Other researchers claim they have not been able to associate this syndrome with Terramaster. I have not been able to make a direct cause and effect tie to Terramaster with this problem, even though I have seen it much worse in some Terramaster-treated bays compared to adjacent untreated bays. However, observational data from some on-farm visits this spring correlate with Terramaster enhancing or predisposing the plants to these developments, especially at higher rates of the EC formulation. However, in all cases I have visited, there was not a true direct comparison between treated and untreated, as confounding factors were always involved.
Please be aware that we see this same set of symptoms developing in bays that have NOT been treated with anything but fertilizer. Follow this example carefully. On Tuesday May 8, we visited a greenhouse in Fayette County (UK's Spindletop Research Farm) to scout for candidate sites to conduct additional tests related to this problem. The roots in all bays appeared to be in excellent health on Tuesday morning, but when we returned on Wednesday morning some bays had nearly every root mass showed the slimy development while adjacent bays were free of it. Except for lifting a few trays on the edge to examine them on Tuesday morning, nothing was done to any of these bays in the past 24 hours and none of these bays had received any fungicide treatments within the water at anytime during this season. We removed some of the trays with their water and treated half on May 8 with Terramaster 4EC at 1.4 oz/100 gallons - carefully measuring the water and the fungicide. This test was conducted under greenhouse conditions and no additional water was added during the experiment. I have examined these plants daily, both visually and with the aid of a microscope and staining, and cannot discern any difference relative to the "slimy-brown syndrome" between the treated and untreated (with 5 replications) as of May 13. In addition, we also treated five outdoor-bays that had excellent root systems without evidence of Pythium root rot or this "slimy brown syndrome" on May 8 with Terramaster 35WP at 1 oz/100 gallons. As in previous experiments, we observed slower root development in treated than in the untreated bays, but no difference in the presence of the slimy rot was evident in either the treated or untreated bays as of May 11. These outside bays had received several rains following treatment, however.
The only consistent factor we find between samples with this "slimy root problem" is an abundance of bacteria both inside the root cells and on their surfaces, regardless of fungicide treatment. Fungal populations are usually low in such roots, where as fungal populations are high when Pythium root rot is present. We see this slimy root problem yearly in the float system, both with and without Pythium. We have not been able to establish that these bacteria are major pathogens in the several tests conducted since 1990 with inoculations into healthy roots using the slimy roots as inoculum, but the slimy root syndrome does develop more rapidly when inoculated into water roots that have been injured than if healthy. Pythium root rot often moves in rapidly following this syndrome, too.
Just a reminder of what we said about Terramaster when it was labeled. "Some crop injury (phytotoxicity) should be expected from use as labeled and the grower/user must accept those risks. It has caused root stunting at the rates labeled in every test I have conducted, and it usually delays plant development by a week or so, plus white veins are sometimes seen at labeled rates. Some specialists say expect it to shock the roots and not to used it except in a rescue situation, which might make sense if roots are always injured when treated. I urge preventive treatments at low rates, based on our many years of research. Remember that Pythium in our area causes very serious "phyto" - stunting and death - but Pythium-infected transplants can lead to serious problems in the field, so count the costs and benefits!"
A number of laboratories are working on this problem and I will keep you posted on the findings.
According to the UK weather center temperature model,
European corn borer moth flight has begun in much of the state.
But weather conditions for mating and egg laying have been
poor across the state. Heavy rains and high winds during the
moth flight period can cause high mortality of the corn borer
moths and reduce levels of this generation. In addition, corn
planting has been delayed in many fields and corn growth has
been slow in others. Most field corn hybrids have a natural
resistance to European corn borer when the plants are less than
about 18 inches in height. Small corn is also less attractive to
corn borer moths for egg laying. We are likely to see some corn
borer activity on other hosts this spring. Generally early
planted
corn has more exposure to the first generation of European corn
borer, and late planted corn is at more risk to the later
generations. These factors indicate that we would expect first
generation corn borer infestations to be lighter on average than
last year at this time.
Predicted date for initiation of moth flight and egg laying.
| Location | Moth flight (550 DD) | Egg laying (750 DD) |
|---|---|---|
| Bardstown | 5/1 | 5/15 |
| Bowling Green | 4/27 | 5/11 |
| Covington | 5/15 | 5/27 |
| Hardinsburg | 5/1 | 5/15 |
| Henderson | 5/1 | 5/14 |
| Lexington | 5/8 | 5/21 |
| Mayfield | 5/1 | 5/14 |
| Princeton | 4/20 | 5/5 |
| Quicksand | 4/25 | 5/13 |
| Somerset | 4/25 | 5/12 |
Generally, first generation corn borer damage results in physiological yield loss. That is, tunneling in the stalk reduces water transport nutrient efficiency and increases the likelihood of some stalk infections. This can reduce grain production by the plant.
The best time to control ECB with foliar sprays is when they are actively feeding in the whorl. This means that they need to be controlled while they are small larvae. Larger larvae leave the whorl and bore into the stalk. Once in the stalk, they cannot be controlled with foliar sprays. For best control, sprays should be directed over the row and downward toward the whorl.
Generally, an action threshold of 50% infested plants with active
larvae in the whorl is used as a guideline for treatment.
However, a more exact economic threshold can be obtained by
using expected yields and grain prices, plant stage, level of
infestation, and cost of control. You can find this threshold in
ENT-49, European corn borers in corn. Producers that have used
Regent at planting will get some first generation ECB protection,
on the order of 60 to 70% control. These fields may still need to
be monitored. Those using Bt corn varieties should have near
complete control of this early generation.
For more information about corn pests, visit "Insect Management Recommendations".
The size of corn is often a critical factor in determining when
it is safe to apply postemergence herbicides. Labels of
postemergence herbicides often use plant height or growth
stage (or both) when discussing timing of applications relative
to corn growth. While this may sound simple, there is come
confusion on how to determine height or growth stage of corn
with respect to herbicide applications.
A common method for determining corn height is done by using free-standing plants. When checking individual plants, measure from the soil surface to the arch of the uppermost leaf that is more than 50 % emerged. Because of the variability among corn plants in the same field, it is better to get an average from several plants than relying on just one plant.
A temptation for some folks is to measure from the soil surface to the tip of outstretched leaves. The measurements by stretching leaves upward and measuring to the uppermost leaf tip often leads to a greater height than intended by the herbicide label.
The collar method is also used to determine the proper timing and method of application of many postemergence herbicides. Staging corn plants in their vegetative growth stage is usually done by counting the number of leaves that have visible collars. The collar is the part of the leaf that joins the leaf blade and leaf sheath and occurs as a discolored line. Collars are not evident until the leaves are well developed and emerged from the whorl; consequently, as you progress up the plant, count only leaves with visible collars and not the uppermost ones that are still in the whorl. For example, a plant may appear to have 5 leaves, but after close examination, it may have only three leaves with visible collars and would be considered in the V3 growth stage.
The first true leaf that emerges during seedling development is characteristically oval-shaped and is the reference point for counting leaves. Once plants reach stage V5 (5 leaves with visible collars), the leaf and ear shoot initiation will usually be complete and a small tassel is initiated in the stem apex tip (i.e. growing point). During tassel initiation, corn will be approximately 8 inches tall and the growing point will be just at or beneath the soil surface. Once plants reach V6, the growing point and tassel will be above the soil surface and the stalk elongation will be rapid. The growth of the stalk and nodal roots will eventually result in the tearing and deterioration of the lowest leaves, thus making it difficult to accurately determine the growth stage.
Staging corn plants that are beyond V6 is possible but may require some practice to become efficient. Dig a plant and cut the stalk lengthwise through the root area. Check for the first elongated internode, which is usually about one centimeter (0.4 inch) in length. The first node above this internode is generally connected to the 5th leaf. Once the 5th leaf has been determined, then use it as the reference point for counting to the uppermost visible leaf collar.
The use of drop nozzles can limit the risk of injury from certain herbicides, especially as the corn canopy develops. Directed applications help in some instances by keeping the herbicide from being intercepted in the top of the canopy where it can be funneled into the whorl and increase exposure to the growing point. This is particularly a problem with certain sulfonylurea herbicides. In cases involving contact herbicides such as Gramoxone MAX, the directed sprays must be fairly precise to limit the amount of contact with the corn plants.
The recommended timings for several postemergence herbicides used in field corn are summarized in the following table. Always check the product label for specific directions.
| Table 1. Timing of Postemergence Herbicides Relative to Corn Growth | |
|---|---|
| Herbicide | Recommended Ranges or Maximum Corn Heights / Growth Stages |
| Accent | Broadcast up to 20" tall or 6 collars (V6). Apply with drop nozzles when corn is between 20" to 36" tall. Do not apply when corn exceeds 30" tall or has 10 or more collars. |
| Accent Gold | Recommended Ranges or Maximum Corn Heights / Growth Stages: Up to 12" tall or 6 collars (V6), whichever is more restrictive. |
| Aim | Up to 8 leaf collar (V8) |
| Atrazine | Up to 12" tall. |
| Basis Gold | Up to 12" tall |
| Beacon | Broadcast between 4" to 20" tall. After corn is 20" tall or exhibits more than 6 collars (whichever occurs first) use directed applications. Apply before tassel emergence |
| Buctril | Prior to tassel emergence |
| Callisto | Broadcast on corn up to 30" tall or up to the 8-leaf stage stage of corn growth, whichever occurs first |
| Celebrity Plus | Broadcast 4" to 20" tall |
| Clarity or Banvel | At 1pt/A rate: 5th leaf stage or 8" tall whichever is more restrictive. At 0.5 pt/A rate: 8 to 36" tall, if 6 leaf is emerging, or 15 days before tassel emergence. Use directed application if: 1) Corn leaves limit spray coverage of weeds, 2) Sensitive plants are nearby, 3) Tank mixing with 2,4-D |
| 2,4-D | Broadcast before corn exceeds 8" tall. Use directed applications when corn is >8" tall and before tassel emergence |
| Distinct | 6 oz/A rate: corn 4" to 10" tall. 4 oz/A rate: corn 10" to 24" tall |
| Exceed | Broadcast between 4"and 30" tall. To limit injury apply, apply with drop nozzles when field corn is 20" to 30" tall or exhibits more than 6 collars V6 (whichever occurs first) |
| Max | Do not apply broadcast overtop corn. Apply only as a directed treatment after smallest corn is 10" tall |
| Gramoxone | Broadcast spike stage up to 20" tall or V6 stage, whichever occurs first. Use drop nozzles for corn 20" up to 36" tall |
| Liberty (LL-corn) | Broadcast on corn up to 20" tall or 7 collars (V7), whichever comes first. Apply with drop nozzles for corn 24 to 36" tall |
| Liberty ATZ (LL-corn) | Up to 12" tall |
| Lightning (Clearfield-corn) | Broadcast on corn up to 20" tall; Use drop nozzles if corn is >20" tall or has 6 or more collars (V6), whichever is more restrictive, or if the crop canopy prevents adequate weed coverage. Do not apply within 45 days of harvest |
| Marksman | Through fifth leaf stage or 8" tall, whichever occurs first |
| Northstar | Broadcast on corn between 4" to 20" tall. Use drop nozzles when corn is 20" (V6) up to 36" tall, whichever comes first |
| Option | Broadcast on corn up to 16" tall or through V5 growth stage, whichever is more restrictive. Use drop nozzles when corn is 16" to 36" tall |
| Permit | Spike through layby |
| ReadyMaster ATZ (RR-corn) | Up to 12" tall corn |
| Roundup UltraMAX or Glyphosate (RR-corn) | Through V8 stage or 30" tall whichever occurs first |
| Spirit | Broadcast on corn between 4" to 24" tall. Use drop nozzles when field corn is 20" to 24" tall or exhibits more than 6 collars (V6), whichever is more restrictive |
| Steadfast | Apply to corn up to 12" tall or exhibiting 6 collars (V6), which is more restrictive |
OPTION is a new foliar herbicide recently labeled by the EPA
for use on field corn. It is a sulfonylurea (ALS inhibitor)
containing 35% of foramsulfuron per lb of product. OPTION is
intended for control of annual and perennial grasses and certain
broadleaf weeds. Broadcast applications of OPTION can be
made from corn emergence up to 16 inches in height or through
V5 growth stage, whichever is more restrictive. Use drop
nozzles when corn is 16 to 36 inches in height. Apply OPTION
at 1.5 oz/A plus a spray adjuvant. A methylated or ethylated
seed oil in combination with a nitrogen fertilizer is
recommended as the spray adjuvant for application. Consult
the OPTION label for optimum weed sizes and the use of soil
insecticides and other precautions.
Fall applications of Princep (simazine) are intended for
controlling certain winter annual weeds prior to planting no-
till corn the following season. While this is the major intent
of this practice, this year's wet spring has forced some growers
to consider planting soybeans instead of corn. The question
now is "Are there risks in switching to soybeans instead of
corn, where Princep was applied last fall?"
The answer is "YES there are risks because soybeans can be injured with Princep at levels as low as 0.15 to 0.2 ppm." Since we have not had any experience in planting soybeans following fall applications of Princep, we do not know to what extent these risks exist. However, it is worth noting that results of soil sampling that we did in a few grower's fields in the spring of 2000 and 2001 indicated that the vast majority of the Princep dissipated within 3.5 to 5 months following fall- applications.
The highest level Princep we observed in a grower's field was 0.12 ppm in soil collected in mid-March (this equates to approximately 0.12 lb ai/A, assuming you sample the top 4 inches of soil). The grower involved in this particular case indicated he applied Princep at a rate of 1 qt/A (1 lb ai/A) December 2nd. Based on that sample we estimated that 88% of the applied Princep had dissipated. That particular situation had a soil pH of 7.4 which is fairly high, and causes greater persistence of the simazine.
It is important to note that the 0.12 ppm is an average concentration for multiple cores collected across the field; consequently, there were probably areas where the Princep concentration exceeded 0.12 ppm. The logical places for excessive levels of herbicide would be the turn rows or other areas where spray overlap occurs.
While it is difficult to know the exact risks for planting soybeans this spring in these situations, it is probably not all that great for many cases in Kentucky, particularly since this past winter had mild temperatures and plenty of soil moisture for herbicide dissipation.
Here are some thoughts that may help growers make a decision on planting corn or soybeans after applying Princep last fall:
1) Plant Corn Until Late May: It is still NOT too late to plant corn. While yield potential starts declining in Kentucky after May 10 (depending on location), significant yield reductions normally do not occur until late May to early June.
2) Grower Accepts the Risk of Soybean Injury: While the Princep label for fall applications is intended for corn, it is perfectly legal to plant soybeans the following spring. However, the grower assumes the risk of soybean injury
3) Check Weed Cover: If you see any weeds present that should be killed by simazine (examples include lambsquarters, pigweed, common ragweed) then the risk of soybean injury is probably minimal. Chickweed and henbit should have been killed long ago. If these winter annuals survived, then it is unlikely there is very not much simazine remaining in the soil.
4) Check pH If soil pH is high (i.e. greater than 7.0) then the risk of injury from simazine carryover will be much greater, compared with soils with a lower pH.
5) Chemical Analysis: Collect soil for chemical analysis of simazine. The procedure for collecting soil for herbicide analysis is similar to that used for nutrient analysis. Collect several cores from random sites in the field to a depth of 4 inches. Combine and mix the cores thoroughly and allow the soil to air dry. UK Regulatory Services at Lexington conducts an analysis of triazine (ie atrazine and simazine) herbicides for a $ 25.00 fee. Contact the county Extension office for more details for collecting soil for triazine analysis.
6) Till Soil Where Feasible: Tillage to a depth greater than 4 inches can help dilute the herbicide concentration, but likewise, it increases soil erosion and defeats the purpose for no-tilling.
Pea aphids and spittlebugs are sap feeders that thrive during
cool, wet springs. The light green pea aphids can be found in
clusters on plant stems and terminal buds. Use of an insecticide
to control them might be justified if alfalfa foliage is yellow
and wilting and there is an average of 50 to 75 aphids per stem. If
many aphids are present, you may see bloated, straw-colored
aphid mummies that have been parasitized by a tiny wasp. The
wasps and hotter weather will reduce aphid numbers naturally.
Spittlebugs overwinter as eggs inserted between the sheath and
stem of grasses. They are most common in mixed grass and
alfalfa stands. The nymphs, or immature stages, excrete a frothy
liquid that covers them completely, providing protection from
drying out and may provide some protection against natural
enemies that prefer to look for food that isn't covered with
spit.
An average of one or more spittlebugs per stem is needed to
justify concern. Even then, the spittle probably provides
protection against and insecticide spray, reducing the
effectiveness of any attempted control measure.
Here is a brief update on the current wheat disease
situation in Kentucky
Rusts: Leaf rust is fairly widespread, but at generally low levels. I have not seen, or heard any reports about stripe rust appearing in the state.
Powdery Mildew: As usual, there is quite a bit of mildew in susceptible varieties throughout the state. The weather conditions have encouraged movement of the disease onto the upper canopy in some fields.
Speckled leaf blotch: This disease is very widespread; it got a good head start earlier this spring as it "jumped" into winter-killed lower leaf tissue. I have seen quite a few fields where speckled leaf blotch has moved into the flag leaf, but the severity is low. This disease should shut down soon assuming we get the standard warming of temperatures during May.
Nodorum leaf blotch: This disease is at high incidence in many fields, but the severity is low. If wet and warm weather occurs during May, look for this disease to be a significant player in reducing yields.
Tan Spot: Levels of tan spot are rather low at this time.
Barley Yellow Dwarf (BYD): BYD has appeared rather late in many fields. Most infections appear to have occurred in the spring, based on the appearance of symptoms during heading. It appears as though fields that were sprayed earlier this spring have significantly less BYD than fields that did not receive an insecticide treatment (for control of aphid that spread the BYD virus). Because of the lateness of symptom expression in most fields, I do not anticipate that serious yield losses will occur, even where no insecticide sprays were applied.
Head Scab: It is too early to know how severe this disease will be this spring. Some varieties were flowering during a rainy period, but the temperatures were cool. These weather conditions are borderline in regards to encouraging infection by the head scab fungi.
Downy Mildew: We are seeing more than usual downy mildew so far this spring. But the disease is almost always confined to small, extremely wet spots of fields. Edges of fields, in particular, appear to be the most affected, probably due to soil compaction issues.
Powdery mildew. Symptoms of powdery mildew are visible now on leaves and shoots of apples and crabapples. Powdery mildew, caused by the fungus Podosphaera leucotricha can seriously reduce the vigor and productivity of apple trees. The mildew fungus may deform, stunt, or kill twigs, leaves, blossoms, and fruit. Signs of the fungus in the form of gray felt-like patches occur on leaves and on current seasons twig growth. Leaves may be distorted, appearing crinkled, folded lengthwise, and thickened. Mildew infections on fruit can result in net-like russetting symptoms. Mildew overwinters in infected buds. It especially survives well through mild winters such as the one just past. Conidia from these primary infections become available to cause new infections in early spring before the apples bloom. Commercial growers are urged to manage powdery mildew with fungicides as described in the Kentucky Commercial Tree Fruit Spray Guide, ID-92, available at county extension offices.
Cedar apple rust. Wet weather a few weeks ago favored production of cedar apple rust (Gymnosporangium juniperi- virginianae) spores on cedars and junipers and favored infection of developing apple leaves. Rust symptoms on apple leaves are just now appearing as tiny bright-orange spots on the upper leaf surface. As the fungus in the spots matures, produces specialized spores, and mates with nearby apple rust, the spots will eventually enlarge and form spore- bearing structures on the leaf undersides. These spores, called aeciospores will infect cedars and junipers in mid- summer to continue the disease cycle on the alternate host. It is too late to apply fungicides for management of cedar apple rust on apples because the period for infection by spores carried from cedars is past.
Large patch disease caused by certain strains of Rhizoctonia solani is commonly a serious problem on zoysia. Between what I have seen and diagnosed and the reports I am hearing, this is the worst year for this disease in the 12 years I have been in Kentucky. This is probably related to the generally mild, wet conditions experienced through much of autumn, winter, and spring.
Suggestions for control include improving drainage in affected fairways by filling low areas or installing tile drainage. Avoid overirrigation, especially in spring and autumn, and avoid adding nitrogen fertilizer in September. Large patch is less severe at higher mowing heights, so on fairways, raise the mowing height by 0.25 inch in mid-to late- September.
Bermudagrass is less susceptible to the disease, and usually damage from the disease is mild enough that it provokes very little concern. Last week, we diagnosed rather severe cases of it on bermudagrass fairways in Louisville and Evansville. According to digital images provided, the appearance of the disease was typical of what we see on zoysia: somewhat circular patches of up to 10-20 feet in diameter, with moderate to severe thinning of turf throughout the patch and an orangish-brown border where the disease has recently been active. Laboratory inspection confirmed the presence of Rhizoctonia solani. In one case, the leaf spotting and melting out pathogen Bipolaris cynodontis was also present, which complicates the situation for the superintendent, but the primary problem was large patch disease.
Normally the most important time to treat with fungicides for large patch is in the autumn: an initial application when thatch temperatures drop below 70 F, usually in mid- to late- September, with a follow-up application sometimes being made later in the autumn. If autumn applications are made, springtime applications typically provide no additional benefit. Rainfall during the past 30 days has been well above normal for the entire state and northward, which has favored continuing disease activity in swards where the disease has evident been active since last autumn. Long-term weather prediction is exceedingly difficult, but current predictions for Central Kentucky are for above-normal rainfall through June. Given the severity of the outbreaks observed on both bermudagrass and zoysia, I believe it is probably justified to spot-treat affected areas of swards with fungicides. This would help to suppress active fungal growth like we observed in the samples sent to us, and it would allow new tillers to grow without risk of infection. Of the available and effective fungicides, PCNB is probably the least costly, and label guidelines do allow its use for a curative spring application. For treatment next autumn, the most efficacious options include Heritage, PCNB, Bayleton, and Prostar; Banner MAXX is a good choice, also.
It has been reported that Bayer has submitted a request to EPA to cancel all uses of fenamiphos, the active ingredient in Nemacur nematicide. This request proposes a three-year phaseout for the chemical.
Nemacur is used for control of nematode diseases in turfgrasses on certain golf courses in Florida and perhaps in certain isolated instances in other states. However, my own experience with turf diseases in Kentucky suggests that nematodes are a minor to nonsignificant component of turf problems in the Commonwealth. Therefore, I do not expect this cancellation to significantly affect disease control in turfgrass in Kentucky.
Kathy Keeney, McCracken Co Horticulture Agent, reported
the beginning of Brood XXIII emergence. This is a 13-year
brood that occurs primarily west of I-65 in Kentucky.
The individual life cycle of the periodical cicada is long but relatively simple. Adults usually emerge between late April and early June. Just before emergence, cicadas burrow to the soil surface and if in water-soaked ground will often build a 6" to 8" tall mud "chimney," a structure very similar to those built by crayfish on water-soaked ground. This structure probably allows the cicadas to climb above the moist ground so their outer skin can dry out and be shed.
Following emergence, adults move immediately to any convenient vertical object and shed their last nymphal skin. They leave empty brown skins, which have split down the back, lying all about. After struggling out of the pupal skin, adult cicadas rest on that site for several hours until their bodies and wings have expanded and are dry and hard.
After mating, females disperse to lay eggs. They prefer grapevines and oak, hickory, apple, peach and pear trees for egg-laying. They first slit the bark and then insert a row of eggs into the wound. Eggs hatch in six to eight weeks. Nymphs fall to the ground and burrow down to the root system where they stay for the next 13 years. Damage occurs as they use their piercing- sucking mouthparts to feed on sap in the roots.
More information on this insect, including control
recommedations, is available in Entfact 446.
http://www.uky.edu/Agriculture/Entomology/entfacts/trees/ef446.htm
Sycamore anthracnose. Anthracnose symptoms have become noticeable on Sycamore in the past week. On infected green, expanding leaves, look for irregular dark, necrotic blotching centered along the leaf veins or leaf edges. These dark blotches may turn a tan color as the diseased areas of the leaves dry out. In the same trees, tips of young shoots with newly expanding leaves are wilting and dying because of twig or shoot infection. With continued rainy weather, the disease should continue to spread in the foliage. Symptoms are not as severe as we see some years when trees are heavily defoliated by now. The incidence and severity of anthracnose diseases of landscape trees varies with the season. When we have cool springs with extended periods of wet weather, antracnose diseases are worse. This spring, much of the wet weather has occurred later in the spring when temperatures were warmer. As the weather dries, sycamores normally put out new, healthy foliage. However, the legacy of crooked branches (because lateral shoots take over when terminals are killed by anthracnose) and multiple shoots arising from the base of a killed branch may be still visible many years later. Sycamore anthracnose is caused by the fungus Apiognomonia veneta, and the fungus attacks both sycamore and London plane.
Ash anthracnose. Brown blotches along leaflet edges can be seen now on new ash foliage. Many of these infected leaflets will begin to drop soon and carpet the walks and lawns nearby. Ash anthracnose is not normally a threat to ash tree survival, however, and the ash trees will simply put out a new set of leaves. The ash anthracnose fungus is a species of Discula.
Maple and oak anthracnose. Symptoms on these trees range from leaf spots to shoot blight and shoot cankers. Maple anthracnose may be caused by Discula sp. or Kabatiella apocrypta, and oak anthracnose by the fungus Apiognomonia quercina. Although these two diseases are less common than the sycamore and ash anthracnose disease, they, too are found in cool, wet springs. Dogwood anthracnose, caused by the fungus Discula destructiva is only found occasionally in most home landscapes, but it is very common in forest trees and heavily shaded landscapes.
Forest tent caterpillars are feeding heavily on a variety of
trees including sweetgum, oak, birch, ash, maple, elm and
basswood. This species is similar to the eastern tent
caterpillar in some ways but its activity pattern does not
appear to fit the MRLS scenario. While classified as a tent
caterpillar, these insects do not make large, obvious tents but
lay down a silk mat on the trunk or branch of a tree on which
to rest and molt.
This caterpillar can be distinguished from the eastern tent caterpillar by the keyhole-shaped spots along its back. Full-grown larvae have light-blue heads speckled with black and are sparsely covered with fine, whitish hairs. There is one generation per year.
May beetle is a generic term for a large group of " to 3/4 inch
long light brown to dark brown beetles that emerge in May or
early June. The adults of many species don't feed but those of
other species can strip the foliage from oaks, and some other
trees. The adults feed at night eating the leaf tissue and
leaving only veins. This means the damage appears suddenly
with no apparent cause. Caterpillars can cause this type of
injury but they should be found on or near damaged leaves.
The beetles fly in, feed, and move away with no trace. Small
trees can be protected with an application of Sevin, if
necessary.
Caterpillar hunters are large (1.25 inch long beetles) with
metallic green wing covers and a blue black head and
following segment with copper edges. The long legs and
antennae are also blue black. These ground beetles were
introduced into New England from Europe to help with
control of the gypsy moth in 1905. The insect has spread
widely in the US. The adult will eat several hundred
caterpillars during a life span of two to four years. They are
common crawling in wooded areas now.
Lone star ticks were identified from cattle in Daviess and
Hopkins counties last week. These ticks are a significant
problem on cattle in western states but they apparently have
been of minor significance so far in Kentucky. They also
infest deer and a number of other wild animals but most of
our problems have been with tick bites on humans.
There are several options for tick control on beef cattle. Most of the sprays listed in ENT-11 for pasture fly control will reduce tick numbers. These are contact insecticides so spray coverage has to be thorough (" to 1 gallon of finished spray per animal. Pour-on insecticides may provide some reduction, depending upon where the lice are attached.
Most insecticide ear tags have Gulf Coast and spinose ear ticks on the label. These tick species attach and feed in the ears of cattle so the tags work well against them. The lone star tick can attach in many places on the animal where insecticide transferred from the ear tags cannot reach them as well. Feed through larvicides in lose or block minerals that contain an insect growth regulator (IGR) or insecticide such as Rabon do not have a systemic effect so they will not affect attached ticks.
Lone star or American dog ticks will attach to horses also. Daily grooming and removal of ticks is one of the best ways to keep numbers down. Repellents containing the active ingredient permethrin are very effective and can be wiped onto the head, neck, legs, and belly.
Application of an insecticide for tick control is generally not feasible. Habitat modification is considered to be the most permanent approach to tick management. Ticks need to be in humid areas to survive. They tend to be most common in grassy, brushy, wooded, and shaded areas. Regular mowing will allow more sunlight to penetrate to the soil surface will and make the area less suitable for ticks over the long run.
Small mammals provide needed blood meals for early stages in the tick life cycle. Removing brush, wood piles, and overgrowth from pasture areas will help to decrease rodent nesting areas and increase pressure from predators. This can help to decrease tick populations, also.
For more information about livestock pests, visit
"Insect Management Recommendations".
Samples diagnosed during the past week in the PDDL have included stinkbug damage and herbicide injury on corn; herbicide injury on wheat; angular leaf spot, bacterial blackleg, Pythium root rot, Rhizoctonia root/stem rot, target spot, and chemical injury on tobacco.
On fruits and vegetables, we have diagnosed fireblight on apple; leaf curl on peach; anthracnose on pear; Pythium root rot on broccoli; and manganese toxicity on tomato.
On ornamentals and turf, we have seen stem rot (Colletotrichum) on petunia; calcium deficiency on lily; fungal canker on clematis; canker (Leptosphaeria) and rosette disease on rose; anthracnose on ash; Phytophthora root rot on cypress; tip blight on pine; Rhizoctonia large patch and Bipolaris leaf spot on bermudagrass; brown patch on ryegrass; Pythium root dysfunction on bentgrass; and red thread on tall fescue turf.
UKREC-Princeton, KY, May 3 - 10| Black Cutworm
| 9
| True Armyworm
| 15
| Corn Earworm
| 40
| European Corn Borer
| 5
| Southwestern Corn Borer
| 1
| | |
NOTE: Trade names are used to simplify the information presented in this newsletter. No endorsement by the Cooperative Extension Service is intended, nor is criticism implied of similar products that are not named.
Lee Townsend
Extension Entomologist
